1. Field of the Invention
This invention relates to a medium stacker apparatus for stacking discharged media and, more particularly, to a medium stacker apparatus incorporated in, e.g., a page printer.
2. Description of Related Art
Conventionally, some printing apparatus or the like have a structure for stacking delivered media on a top of the top cover to make the apparatus compact. With these apparatuses, the top cover is provided pivotally movably, and therefore the apparatus interior is easily accessible by opening the top cover by ninety degrees or more in the case where obstruction such as printing medium jamming during printing occurs or where consumable parts are to be replaced.
FIG. 12 is an external view showing a conventional printing apparatus, and FIG. 13 is a schematic side view showing an inside of the conventional printing apparatus. As shown in FIG. 12 and FIG.13, a top cover 2 is formed at a printing apparatus housing, and the top cover is in a pivotally movable state around a pivotal center 3 as the center. A stacking portion 4 for stacking printed printing media, is formed at the top cover 2, and a distal end 5 of the stacking portion 4 is formed as projected in a substantially vertical direction so as to prevent the printing media from falling inside the apparatus 1. A cutout portion 6 is formed at the distal end 5, and an ejection roller 7 is arranged at the cutout portion 6. The ejection roller 7 is revolvably formed on the apparatus housing 1. A pressure roller 8 is formed at the top cover 2 as facing to the ejection roller 7.
An exposure head 9 is formed below the top cover 2 and is located at a prescribed position on an image formation unit 10 in a state that the top cover 2 is closed as shown in FIG. 12. A position of the exposure head 9 is set as substantially the same in a horizontal direction as a position of the pivotal center 3 of the top cover 2. This is for positioning accurately the exposure head 9 because the position of the exposure head 9 is set by closing the top cover 2. A fixing unit 11 is arranged below the stacking portion 4 of the top cover 2.
The ejection roller 7 and the pressure roller 8 discharge and stack the printed media on the stacking portion 4 of the top cover 2. With the apparatus shown in FIG. 12 and FIG. 13, the top cover 2 is made opened after the printing media thereon are removed where the top cover 2 is to be opened while the printing media are stacked. This is because the printing media may drop and be scattered where the top cover 2 is intended to be opened without removing the printing media.
To prevent the above, that is, to prevent the printing media on the top cover from falling in where the top cover is opened, a paper delivery apparatus having a member holding printing media when the top cover is opened has been invented, and the apparatus is as disclosed in, e.g., Japanese Patent Application Publication No. JA-7-315,670.
Disclosed in the above Publication is that a paper holding member is pivotally formed at an upper cover, that the paper holding member is positioned as separated from the upper cover when the upper cover is closed, and that the member presses a paper receiving table for stacking papers when the upper cover is opened.
With this conventional apparatus described above, however, the distal end 5 of the stacking portion 4 as shown in FIG. 12 needs to be deeply formed in a case where a large number of the printing media are stacked on the stacking portion 4 of the top cover. However, if the distal end 5 of the stacking portion 4 is deeply formed, the distal end 5 hits the shaft of the ejection roller 7. Accordingly, there raises a problem that the distal end 5 of the stacking portion 4 cannot be deeply formed. This problem will be briefly explained with referring to FIG. 14 and FIG. 15.
FIG. 14 is an operation illustration in a case where an end 4b of the stacking portion is comparatively shallowly formed, and FIG. 15 is an operation illustration in a case where the end 4b is deeply formed. In FIG. 14, a stacking portion 4a of the top cover and a medium stopping portion 5a are pivotally moved in a direction of an arrow around a pivotal center 3 as a center. In this situation, as showed by a dotted line, the medium stopping portion 5a can pass over a shaft 11 of an ejection roller 7, so that the top cover is movable up to a predetermined position with the medium stopping portion 5a not in contact with the shaft 11. To the contrary, in FIG. 15, where the medium stopping portion 5a is deeply formed, the medium stopping portion 5a interferes with the shaft 11 of the ejection roller 7 as showed a dotted line, so that the top cover is not pivotally movable up to the predetermined position. As described above, it is difficult to form the end 4b of the stacking portion 4a deeply, so that media of a certain amount or more cannot be stacked.